Radial variable displacement hydraulic motor of the slow type

ABSTRACT

A RADIAL VARIABLE DISPLACEMENT HYDRAULIC MOTOR OF THE SLOW TYPE IS DISCLOSED, IN WHICH THE CHANGE OF THE EFFECTIVE DISPLACEMENT IS OBTAINED THROUGH A CHANGE OF THE STROKE OF THE PISTION WITHIN THE CYLINDERS BY A CHANGE OF THE ECCENTRICITY OF THE ECCENTRIC CONTROLLING THE CONONECTING RODS OF SAID PISTONS, SAID CHANGE BEING OBTAINED BY THE ECCENTRICITY OF THE ECCENTRIC CONTROLLING THE CONNECTING RELATIVE CHANGE OF POSITION OF MOUNTING OF TWO COAXIAL ECCENTRICS COUPLED TO THE ENGINES SHAFT.

5 Sheets-Sheet 1 R. CAVALIER! fi/ccnmoo Cnmum/ 'Otl 5,1971

RADIAL vmmama nxsrmcmnm n'mnwuc MOTOR OF THE SLOW TYPE Filed April 21. 1969 Oct. 5, 1911 R. CAVALIER! 3,610, 0

RADIAL VARIABLE DISPLACEMENT HYDRAULIC MOTOR OF THE SLOW TYPE Filed April 21. 1969 5 Sheets-Sheet 2 INVENTOR f/ccnma farm mm BY 5* JM ATTORNEY Oct. 5, 1971 R. CAVALIER! 3,610,106

RADIAL VARIABLE DISPLACEMENT HYDRAULIC MOTOR OF THE SLOW TYPE F11! April 21. 1969 5 Sheets-Sheet 5 a a, "if e r-- 19 I A /ccmw a CA 4444 154v BY W WM ATTORNEYS "Oct. 5,1971 RCAVALIERI 3,610,106

RADIAIJ VARIABLE DISPLACEMENT HYDRAULIC MOTOR OF THE SLOW TYPE Filed April 21. 1969 5 ShBBtS-Shflfit INVENTOR Flea/M00 (.4u)u/x/ BY r- JAG Wu ATTOR NEE Oct. 5; 1971 R. CAVALIERI 3,610,106

RADIAL VARIABLE DISPLACEMENT HYDRAULIC MOTOR OF THE SLOW TYPE F1 1ed April 21. 1969 5 Sheets-Sheet 5 z & J1 9 z ///z/// 9 8 A O \wqwl/ INVENTOR A /ccmwo Cn VAL/5m BY J/ w cw ATTORNEYS United States Patent Ofice 3,610,106 Patented Oct. 5, 1971 3,610,106 RADIAL VARIABLE DISPLACEMENT HYDRAULIC MOTOR OF THE SLOW TYPE Riccardo Cavalieri, 29 Viale Pola, Rome, Italy Filed Apr. 21, 1969, Ser. No. 817,733

Claims priority, application Italy, Apr. 30, 1968, 36,660/68; July 6, 1968, 38,246/68; Dec. 21, 1968, 42,152/68 Int. Cl. F0111 1/06 U.S. Cl. 9212.l 8 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a hydraulic radial motor of the slow type, the displacement of which is variable, and more specifically this invention relates to a device for changing the effective displacement of a motor of this type, operating through the reduction of the strokes of the pistons within the cylinders, by means of the change of the eccentricity of the eccentric controlling the connecting rods of said pistons.

It is known that the heaviest limitation of use of hydrostatic drives in vehicles, is due to the difiiculty of conciliating the requirements of the high thrust torques with those of the high speeds.

This derives from the fact that the high torques require the use of large displacement hydraulic motors. while the high speeds require the use of motors having a reduced displacement.

At the present status of the art, the slow hydraulic motors, i.e. those motors which are capable of being directly coupled to the driving wheels, with the interposition of no train of reduction gears, are the fixed displacement, radial type motors.

The main purpose of the present invention is that of providing a slow radial hydraulic motor, with a single radially disposed series or plural radially disposed series of cylinders, including means for changing its displacement, so as to render the motor capable of being adapted to the various operative exigencies which will occur during its operation.

More particularly, the purpose of the present invention is that of providing means for changing the effective displacement, in the radial hydraulic motors, including means for changing the total eccentricity of an eccentric element coupled to the pistons of the radial motor in compliance with the displacement as required during the particular stages of operation.

According to the present invention, the change of the eccentricity of the eccentric controlling the pistons is obtained by changing the mutual position of mounting of two eccentric elements coaxially located the one within the other, so as to effect a total eccentricity resulting from the vectorial sum of the single vectors representing the eccentricities of said two eccentrics.

It results, accordingly, that the total eccentricity will be maximum when the two vectors representing the eccentricities of said two eccentrics are located along the same axis and are both directed in the same direction; on the contrary, a minimum eccentricity will be obtained when the two vectors, representing the eccentricity of said two eccentrics, are both located along the same axis, being however directed in opposite directions.

The relative rotation of the two eccentric coaxial elements will be obtained, according to this invention, by means of an annular cylinder formed by a toroidal groove provided either on one of the coaxial elements or on both elements. In this groove, a first contrast element and a second contrast element, each rigid with one of the two coaxial parts, form the piston and the bottom of cylinder itself, respectively. When a pressurized fluid, for instance oil. is sent on either side of the contrast element rigid with the supply and exhaust ducts for the oil, the mutual rotation of the two coaxial elements will be obtained, in either direction, initiating the change of the relative orientation of the vectors representing the single eccentricities, so as to obtain the required change of the total eccentricity.

During the normal operation of the hydraulic motor according to this invention, said two coaxial eccentric elements are held rigid by means of a device which can allow the elements to be locked at any mutual angular position, allowing thus an almost continuous variation of the total eccentricity to be obtained.

The locking element as above referred to, consists of an annular element slidable in a space defined between the opposed surfaces of the outer eccentric and of the inner eccentric with a double, inner and outer set of splines so arranged that the outer splines will engaged corresponding splines provided inside the outer eccentric element, and the inner splines will engage similar splines provided on the outer surface of the inner eccentric element.

By the axial displacement of said locking element, the disengagement thereof will be obtained from one of the two sets of splines, preferably from the set of splines of the outer eccentric coaxial element allowing thus the disengagement of the two eccentric elements.

This is obtained by making of different lengths the two splined clutch members provided in the inner and outer eccentric elements so that when the coupling of the locking element with the shorter splined element will cease, the other element will be still engaged.

In order to facilitate the engagement of the splines during the coupling stage, the teeth are preferably beveled in correspondence with the associated ends.

The operation of change of the displacement, i.e. of change of the total eccentricity of the eccentric element controlling the pistons, consists of an operation of change of the orientation or relative position of mounting of the two eccentric coaxial elements. and is carried out by means of a control device ensuring the sequence of the operations in the required order, and rendering impossible the start of a subsequent stage until the preceding stage has been completed.

The stages of this operation can be summarized as follows:

(1) Unlocking operation of the two coaxial eccentric elements, effected by the axial displacement of the annular element until the mutual disengagement of the two c0 axial eccentric elements occurs.

(2) Operation of mutual rotation of the two eccentric coaxial elements.

(3) Relocking operation, effected by the return of the annular element to its clutching position with both eccentric coaxial elements.

The arrangement according to the present invention will be described with reference to an embodiment particularly suitable for obtaining two predetermined values of total eccentricity, resulting from the vectorial sum and the difference, respectively, of the eccentricities of the two eccentric coaxial elements (maximum displacement and minimum displacement, respectively). The two eccentricity values can be taken at will, provided that they are comprised between the maximum value and the minimum value as previously specified, by effecting mutual rotation through different angular values.

The present invention will now be described with reference to a preferred embodiment thereof, as shown in the attached drawings, wherein:

FIG. 1 shows a diagrammatical cross sectional view of a radial hydraulic motor, according to this invention;

FIG. 2 shows a cross sectional view taken along the planes 22 of FIG. 1;

FIG. 3a, 3b, 30 show the respective positions which can be taken by the eccentric elements controlling the pistons of the radial motor in the conditions corresponding to the maximum, minimum and intermediate displacements (eccentricities);

FIG. 4 shows a cross sectional view of the eccentric unit controlling the pistons;

FIG. 5 shows a cross sectional view taken along the plane 5-5 of FIG. 4;

FIG. 6 shows a cross sectional view taken along the plane 6-6 of FIG. 4;

FIG. 7 shows a cross sectional view taken along the plane 77 of FIG. 4;

FIG. 8 shows a longitudinal sectional view of the annular coupling element for the eccentrics controlling the pistons;

FIGS. 9a and 9b show the detail A of FIG. 4 on an en larged scale;

FIG. 10 shows the detail B of FIG. 5 on an enlarged scale;

FIG. 11 shows the detail C of FIG. 6 on an enlarged scale; and

FIG. 12 shows the detail of the structure of an auxiliary element of the hydraulic control for changing the eccentricity, corresponding to the detail D of FIG. 4.

With reference to FIGS. 1 and 2, the radial hydraulic motor to which the control arrangement for changing the displacement according to this invention can be applied, includes a frame I, whereon are located the cylinders 2 within which slide the pistons 3 connected by means of the piston rods 4 to an eccentric unit associated to the driving shaft 6.

The eccentric unit 5 includes a first eccentric 7 rigid with the driving shaft 6 and a second eccentric 8 coaxially mounted on the first eccentric in a semi-fixed way, as will be disclosed later on.

With refeernce to FIGS. 3a, 3b, 30, there will be now disclosed the general arrangement of the means for changing the total eccentricity of the eccentric unit 5. In these figures, the reference a denotes the axis of rotation or center of the driving shaft 6, b is the center of symmetry of the first eccentric 7 rigid with the driving shaft 6 and c is the center of symmetry of the second eccentric 8 rotatably mounted on the first eccentric 7.

As it will be noted, in FIGS. 3a, 3b and 3c, the change of the angular position of the eccentric 8 with respect to the eccentric 7 causes a change of the total eccentricity e of the unit 5, the magnitude of which is the length of the sum vector e consisting of the vectorial sum of the vectors corresponding to the single eccentricities e 2 of the eccentrics 7 and 8. This is rendered clear from the three cases shown in these figures which show the conditions of maximum, minimum and intermediate eccentricity, respectively.

With reference, now, to FIGS. 4 and 5, the preferred embodiment of the present invention will be now described, for the control of the total eccentricity of the control element 5 for the pistons of the hydraulic radial motor.

On the periphery of the eccentric 7, rigid with the driving shaft 6, a duct 9 is embodied, defined on one side by a bushing 10 screwed on the body of the eccentric 7 and outwardly closed by the internal cylindrical periphery of the movable eccentric element 8. On the two opposed surfaces of the peripheral channel 9 two splined crowns 11, 12 are embodied and so arranged as to be able to engage a driving ring 13 rigid with an annular piston 14 slidable in said peripheral duct 9'.

The part 9 of the peripheral duct 9 is connected to a duct 15 provided in the eccentric external element 8 which connects at 16 with a branch 17 of the duct 18 provided inside the inner eccentric element 7 and driving shaft 6. The duct 18 through another branch 19 can communicate with the chamber 20 forming an annular cylinder for controlling and allowing the mutual rotation of the eccentric elements 7, 8.

The part 9 of the peripheral duct faced towards the annular piston is connected through a duct 21 to a valve 22 unidirectionally limiting the fluid flow as will be hereinafter described. The duct 21 is connected at 23 to a branch 24 of the duct 25. Another branch 26 of the duct leads to another part, opposite to the preceding one, of the chamber 20 forming the aforesaid annular cylinder. In fact, the chamber 20 is subdivided into two contiguous parts by the contrast elements 27, 28 rigid with the outer eccentric 8 and the inner eccentric 7, respectively.

With reference to FIG. 12, the valve 22 for the one way restriction of the flow of the hydraulic fluid, includes a cylindrical-conical seat within which a conical body is contained, provided with a gauged longitudinal passage 31, restricting the fluid flow when it is directed in the direction of the arrow F, and the element 30 is leftwards pushed; and with passages 32 for the unobstructed passage of the fluid when the flow is directed in a direction contrary to that of the arrow F, and the element 30 bears against the bottom of the seat 29.

In order to understand the operation of the control arrangement for the eccentricity, according to the present invention, it will be suitable to consider first a given mutual position of the two eccentric elements 7 and 8, for instance that shown in the figures of the attached drawings, corresponding to the maximum eccentricity and therefore to the maximum displacement of the hydraulic motor (see FIG. 3a).

Let us assume that minimum eccentricity and therefore minimum displacement is desired. This position will be obtained when the elements 7 and 8 will be in their position moved through with respect to their initial position (see FIG. 3b).

This o eration will be effected by delivering pressurized hydraulic fluid to the duct 18 and connecting the duct 25 to exhaust.

The hydraulic fluid delivered to the duct 18 initially will be unable to effect the displacement of the contrast elements 27, 28 as said displacement will be impeded by the engagement existing between the eccentric elements 7, 8 comprised by the locking ring 13.

The hydraulic fluid delivered to the duct 18 reaches through the branch 17 the space 9 at the right hand side of the annular element 13, and as the chamber 9 is connected to exhaust through the branch 21 and the duct 25, the annular piston 14 will drive leftwards the annular element 13 disengaging the teeth 11, 12 from the eccentric elements 7, 8, respectively, causing the unlocking thereof.

At this point the second stage will start automatically, i.e. that of the mutual displacement of the eccentric elements 7, 8. This operation will be terminated when the contrast elements 27, 28 will come into contact with one another in the position opposite to that shown in FIG. 5. In this final position the communications between the ducts 15 and 21, and 17, 24, respectively, interrupted at the beginning of the mutual rotation of the two coaxial bodies 7, 8 will be restored, however with reversed positions, i.e. the duct 17 will communicate with the duct 21, while the duct 24 will communicate with the duct 15.

Under these conditions, the pressurized hydraulic fluid in the duct 17, passing through the duct 21 will bring again the annular piston 14 rightwards, effecting again the connection of the eccentric elements 7 and 8.

It is now evident that if at this point a reversal of the flow of the hydraulic fluid in the two ducts 18, will be effected, i.e. the pressurized hydraulic fluid will be delivered to the duct 25, while the duct 18 will be connected to exhaust, the cycle of operations will be repeated in the reversed direction.

In fact, starting from the minimum eccentricity position, and delivering pressurized fluid to the duct 18, said fluid will be delivered automatically through the branch 24, also to the right hand chamber 9 embodied in the eccentric body 7. As simultaneously, the similar left hand chamber 9 will be connected to exhaust (said chamber 9 being now connected to the duct 18), the annular piston 14 will be leftwards pushed until it causes the disengagement of the annular element 13 from the splines of the eccentric element 8, causing thus the disengagement thereof.

At this point the second stage will automatically start, i.e. the stage corresponding to the mutual displacement of the two eccentric coaxial elements 7, 8 so as to increase the total eccentricity.

This stage, caused by the pressurized hydraulic fluid in the duct 25, will be discontinued when the two contrast elements 27, 28 will be again in contact in register with the maximum eccentric position, as shown in FIG. 5.

In this final position, the communications between the ducts 15, 21 and 24, 17 respectively, discontinued at the start of the mutual rotation of the coaxial eccentric elements 7, 8 will be restored again, however with reversed positions, i.e. the duct 17 will communicate with the duct 15, while the duct 24 will be put into communication with the duct 21. Under these conditions the pressurized fluid in the duct 24,, passing through the duct 21, will bring again rightwards the annular piston, restoring the con nection between the two eccentric elements 7, 8.

Having thus described the present invention, what is claimed is:

1. A hydraulic motor having a drive shaft, a plurality of cylinder and piston assemblies radially disposed in a series about the drive shaft, a pair of inner and outer eccentrics interconnecting the drive shaft and the pistons, said inner eccentric being rotatable with the drive shaft and said outer eccentric encompassing said inner eccentric, and means for selectively locking the two eccentrics together in a first position relative to each other and for unlocking and rotating the eccentrics relative to each other to a second position and for relocking the eccentrics together in said second position, the last-named means comprising external splines on said inner eccentric and internal splines on the said outer eccentric and means selectively engageable between the splines on said eccentrics to lock the eccentrics in adjusted position relative to each other.

2. A hydraulic motor as claimed in claim 1, and means for selectively moving said engageable means parallel to the axis of the drive shaft thereby selectively to engage and disengage said engageable means.

3. A hydraulic motor as claimed in claim 2, said moving means comprising an annular piston disposed in an annular chamber between said eccentrics, and means for selectively applying hydraulic fluid pressure to opposite sides of said piston.

4. Apparatus as claimed in claim 3, said means for applying fluid pressure comprising a first passageway for hydraulic fluid and means responsive to the application of hydraulic fluid under pressure in said first passageway to disengage said engageable means and to rotate said eccentrics relative to each other in one direction and to reengage said engageable means, and a second passageway for hydraulic fluid and means responsive to the application of hydraulic fluid under pressure in said second passageway to disengage said engageable means and to rotate said eccentrics relative to each other in the opposite direction and to reengage said engageable means.

5. A hydraulic motor as claimed in claim. 4, said passageways having portions extending through said drive shaft and then outwardly through said inner eccentric and registering with portions of said passageways in said outer eccentric.

6. A fluid motor as claimed in claim 8, said restricting means comprising valve means permitting a higher fluid flow rate in one direction than in the other opposite direction.

7. A hydraulic motor as claimed in claim 5, said first passageway comprising a first U-shaped portion in said outer eccentric having open ends extending toward said inner eccentric, the end of said U-shaped portion remote from the portion of said first passageway in said inner eccentric communicating with said chamber at one side of said annular piston, said second passageway having a U-shaped portion in said outer eccentric having its end remote from said first eccentric communicating with said chamber at the other side of said annular piston, said portions of said passageways in said inner eccentric also communicating with opposite ends of a partial annular chamber in said inner eccentric whose ends are separated by a projection on said outer eccentric.

8. A hydraulic motor as claimed in claim 4, and means restricting the flow of said hydraulic fluid in a direction to effect the engagement of said engageable means relative to the flow of hydraulic fluid in the direction to disengage said engageable means.

References Cited UNITED STATES PATENTS 2,750,816 6/1956 Mott 92-13 X 2,836,120 5/1958 Navarro 10338 2,521,711 9/1950 Galliano 103-38 X 2,856,793 10/1958 Budlong 103-38 2,932,255 4/1960 Neukirch 10338 X 3,150,540 9/1964 Neumann 10338 X 3,180,178 4/1965 Brown et a1 92-13 X 3,353,493 11/1967 Feroy 10338 X MARTIN P. SCHWADRON, Primary Examiner L. J. PAYNE, Assistant Examiner US. Cl. X.R. 92-72 

